This application is a competing renewal application of GM62437 that concerns chemical approaches to sorting out the mechanisms, regulation, and functions of acetyltransferase and demethylase enzymes that modify histones and other proteins. p300/CBP histone acetyltransferase (HAT) and LSD1 histone demethylase are key enzymes that regulate gene expression and are potential therapeutic targets in a range of diseases. p300/CBP is a broadly acting HAT that has been implicated in modulating cancer pathways, endocrine disorders, immune signaling, and learning and memory. LSD1 is a transcriptional repressor that removes methyl groups from Lys4 of histone H3. In this application, we plan to build on our recent progress regarding structural analysis of the p300/CBP HAT domain and the LSD1 catalytic domain in complex with our synthetic inhibitors. There are four specific aims: 1) Determine the scope and mechanisms of p300/CBP HAT catalysis and regulation based on the p300 HAT X-ray structure. In this regard, we will investigate the role of the p300/CBP L1 loop and the autoregulatory loop using mutagensis and by employing expressed protein ligation. 2) Develop a new generation of selective small molecule HAT inhibitors and apply these to gene regulation and disease model studies. Virtual ligand screening will be employed based on the crystal structures of p300/CBP HAT and PCAF/GCN5 HAT in complex with bisubstrate analogs. 3) Determine the basis for LSD1 histone demethylase substrate recognition. Chemical and biochemical strategies will be used to discern the potential role of a substrate gamma turn. 4) Develop synthetic inhibitors for the modulation of LSD1 activity in cells and for use in proteomics analysis. Leads will be developed from propargylamine and hydrazine scaffolds. Taken together, these studies have the potential to uncover important insights into the basis of chromatin remodeling and define new directions for pharmacologic intervention. PUBLIC HEALTH RELEVANCE: There is increasing interest in the biology and pharmacology of epigenetics. This application addresses two key enzymes involved in the regulation of epigenetic chromatin remodeling. Insights obtained from this research plan could lead to new therapeutic strategies for cancer, diabetes, immune disorders, and neuropsychiatric conditions.